MECHANISM OF ENVIRONMENT-INDUCED CRACKING

Some media such as hydrogen, sulfides and carbides but also metals are known to be able to embrittle metals. The present paper tries to elucidate this medium-induced cracking (environmental cracking). In regions of current flow (slip bands) a fast transport of foreign atoms may occur along the dislocations in certain temperature ranges. This leads to supersaturation at sites where gliding is stopped. In form of pressure bubbles, as short-time precipitates, the medium inhibits further gliding. For hot cracking and relaxation cracking, the precipitation of the attacking medium (carbide or sulfide) along the grain boundaries represents the frozen-in state of the process of embrittlement.